Ship steering control system

ABSTRACT

An apparatus is provided for steering a ship which replaces the conventional rudder. A circulation is induced around a rounded or bulbous stern producing a lateral force opposite to the direction of the circulation, thereby turning the ship. The circulation may be induced by one or more of the following devices (a) unequal augmentation of the momentum of the boundary layer on the two sides of the ship by water jets flowing from backward facing slots, (b) by the use of a narrow movable vane which fixes the location of the stagnation line on the rounded stern, and (c) by suction slots close to a fixed or movable vane which, by selective suction on one or the other side of the vane, augment the circulation for any given location of the vane.

United States Patent [191 Wald [451 Oct. 16,1973

[ SHIP STEERING CONTROL SYSTEM Quentin R. Wald, Old Lyme, Conn.

[73] Assignee: General Dynamics Corporation, St.

Louis, M0.

22 Filed: Oct.12, 1971 21 Appl.No.: 187,958

[75] Inventor:

[52] US. Cl. ..114/151, 60/231, 115/12 R, 244/52 [51] Int. Cl B63h 25/46 [58] Field of Search 60/221, 231; 115/12 R, 16; 114/151; 239/265.23; 244/50-52 [56] References Cited UNITED STATES PATENTS.

2,699,644 1/1955 Coanda 115/16 3,258,916 7/1966 Lehmann 114/151 X 3,427,809 2/1969 Lavoic 60/231 3,598,078 8/1971 Baer 114/151 Primary Examiner-Milton Buchler Assistant ExaminerStephen G. Kunin Att0meyWilliam C. Everett 5 7 ABSTRACT An apparatus is provided for steering a ship which replaces the conventional rudder. A circulation is induced around a rounded or bulbous stern producing a lateral force opposite to the direction of the circulation, thereby turning the ship. The circulation may be induced by one or more of the following devices (a) unequal augmentation of the momentum of the boundary layer on the two sides of the ship by water jets flowing from backward facing slots, (b) by the use of a narrow movable vane which fixes the location of the stagnation line on the rounded stern, and (c) by suction slots close to a fixed or movable vane which, by selective suction on one or the other side of the vane, augment the circulation for any given location of the vane.

6 Claims, 4 Drawing Figures PATENIEBum 16 ms 3.765.363

sum 2 nr 2 2| FIG?) 1 SI-IIP STEERING CONTROL SYSTEM The present invention is concerned with a novel method of steering a ship which replaces the conventional rudder.

A ship is controlled in the conventional manner by means of a movable rudder at its stern'which, by being turned to an angle relative to the flow of water, produces a direct sideward force at the stern of the ship, thereby causing it to turn. The forces on the rudder are large and powerful steering engines or rams are required to actuate it. Such mechanical systems are susceptible to failure, including the possibility of jamming. Should jamming occur in the course of a turn, it may be impossible to return the ship to a straight path.

I desire to eliminate the. conventional rudder altogether and to steer the ship solely by generating a circulatory flow around the stern of the shipitself by fluidic means.

It has previously been suggested by Norman to employ the jet flap previously studied inaerodynamic research for ship control. Norman (Jet Flaps and Jet Assisted Rudders for Ship Control, Proceedings of the Second Ship Control Systems Symposium, November 1969) uses a jet of water on the trailing edge of a rudder and at an angle to the mainstream to divert the mainstream and cause a substantially increased reactive force on the rudder.

The jet flap uses, however, a substantial amount of fluid for the side thrust generated. Circulation control in aerodynamics has been achieved using a. relatively small flow of air from a slot to reenergize the boundary layer. See, e.g., J. Dunham, A Theory of Circulation Control by Slot-Blowing, Applied to a Circular Cylinder, J. Fluid Mechanics (British), vol. 33, part 3, pp. 495-514(1968). Dunham notes (p. 495) that ajet flap uses perhaps ten times as much air as the circulation control he discusses. Dunham also notes that the pressures at separation of the boundary layer on each side of the cylinder remain equal even when the boundary. layer on one side is energized by slot air. It is this phenomenon that underlies the controlof the circulation of the fluidaround the object, since the flow must be diverted to one side to satisfy this condition in the presence of slot blowing. Experiments confirming this are described by Dunham in the Journal of the Royal Aeronautical Society, Vol. 74(1970).

Similar control of circulation is shown in the aeronautical area by the use of suction. See, e.g., F.O. Ringleb, Investigation of Suction Flaps, Princeton Univ. report No. 304(1955) and D. C. Hazen et al., Circulation Control by Means of Trailing Edge Suction, Princeton Univ. report No. 239(1953). The use of a vane on the rear edge for circulation control has been shown by B. Thwaites (see, e.g., J. Royal Aeronautical Society vol. 52, ll7(l958)).

These principles in the aeronautical area have never been applied to the problem of steering a ship by direct application to the hull without the use of a rudder. I desire to apply the principles to this problem and to provide specific mechanisms for doing so.

In one embodiment of the invention, I achieve my purpose by controlling the relative flow of water from backward facing slots on either side of the ship, increasing or decreasing the velocity of one jet with respect to the other. By augmenting the momentum of the water in the boundary layer more on one side of the v ship, the tendency for the flow to break away from the hull in turbulent eddies is reduced on that side. The consequence is a circulatory flow around the stern tending to encroach on the less energetic and usually separated flow on the other side. A turning force results from the circulating flow. The essential relation between force and circulation is known in fluid mechanics as the law of Kutta and Joukowski. (See, for instance, G. K. Batchelor, An Introduction to Fluid Dynamics, Cambridge University Press. page 406. Circulation is defined on page 93 of the same reference.)

This embodiment does not depend to any major degree on the jet thrust being exerted at a large angle to the general flow (as in a jet flap device or a bow thruster) but amounts to a fluidic control wherein a relatively small amount of energy, applied unequally to the boundary layers on each side, produces a major asymmetry of the flow around the stern and a resulting lateral force. Should the pumping system fail, the flow around the hull quickly returns to a symmetrical pattern and the steering force is automatically removed.

In another emodiment of my. invention I provide a narrow movable vane which controls the line of confluence of the flow from the sides of the ship, known as the stagnation line. When separation is delayed by any suitable devices such as the previously described jets, a vane of small area fixes the location of the stagnation line and thereby controls the circulatory flow around the. stern.

In a third embodiment, a vertical slot is provided on either side of the vane described above. When water is sucked into an interiorchamber through a slot on one side of the vane, the circulatory flow around the stern, and hence the lateral force, is augmented irrespective of the position of the vane. Consequently this third embodiment may employ a fixed vane on the centerline of the ship or a movable vane as in the above described second embodiment. A larger turning force can be developed if a movable vane is employed.

By these embodiments, I have determined that it is possible to steer a ship without a conventional rudder by relying solely on the steering effect of a circulatory flow around a rounded or bulbous stern induced by any of several hydrodynamic means. Such circulation causes a reactive force on the stern of the ship in the opposite direction, thereby providing the steering forces. Such forces are substantially greater than the direct reactive force of any jets which may be employed to induce the circulation. Elimination of the rudder of conventional design eliminates the drag forces associated with such a rudder and eliminates the possibility of a loss of control due to structural failure or of a control jammed in a turning position. If any failure occurs in the fluid control employed in my invention, the ship isleft with a neutral control.

Accordingly, it is an object of my invention to provide a means for steering a ship by inducing a circulation around a rounded stern.

It is a further object of my invention to cause this circulation by jets on each side of the ship which add varying momentum to the boundary layer flow on either side.

Alternatively, it is an object of my invention to cause circulation around the stern by means of a movable vane in combination with some means of delaying flow separation.

Alternatively, it is an object of my invention to cause circulation around the stern by removal of water into a suction slot on one side of a fixed or movable vane.

Those and other objects will become apparent from the following description and the accompanying drawings in which:

FIG. 1 is an underside perspective view of the stern of a ship showing jets around the stern of the ship according to one embodiment of the invention.

FIG. 2 shows a horizontal cross-sectional view of the embodiment of the invention in FIG. 1.

FIG. 3 shows an underside perspective view of the stern of a ship showing an alternative embodiment of the invention.

FIG. 4 shows a horizontal cross-sectional view of the embodiment of the invention shown in FIG. 3.

In FIG. 1 is shown the stern of a ship 11 having an underbody 12 carrying twin screws 13. At the rear of this underbody 12 between the twin screws 13 is a rounded stern portion 14 which in the embodiment of FIG. 1 is fixed in place. This rounded stern portion is in place of the conventional rudder. Between this rounded stern portion 14 and the underbody 12 there is defined a pair of slots 15 extending generally vertically up the side of the underbody l2 and issuing rearwardly.

As shown in FIG. 2, these slots 15 are in communication with plenum chambers 16 within the body of the hull. Since the gap between the rounded stern portion 14 and the underbody 12 is fixed, it will be seen that the velocity of flow of water through the gaps 15 is dependent upon the pressure of the water in the plenum chambers behind them. The pressure of these plenum chambers in in turn dependent upon a valve 17 communicating with both chambers and supplied with water from a hydraulic pump 18 within the ship. Hydraulic pump 18 receives its intake water through a pipe 19 which is shown as leading in from a forward portion of the ship. It will be understood that intake pipe 19 will either draw water from the bottom of the ship or from both sides of the ship. However, this is not critical.

In FIG. 2 are shown the lines of flow of water around the stern of the ship. As shown in FIG. 2, the flow of water out of the starboard side of the valve 17 is greater than that out of the port side of valve 17, with the result that the port gap has lower flow than the starboard gap 15. These two jets of water flow around the rounded stern portion 14 until they come together at a stagnation point which is on the stern of the ship but not on the centerline as would be the case if the two flows were of equal energy. Due to this displacement of the stagnation point by these two minor flows of water around the stern of the ship, the main flow of water around the stern of the ship accompanying the motion of the ship is caused to flow around the stern of the ship, after which it flows on an angle to one side. The transverse momentum accompanying the unbalanced flow of this much larger water flow causes a resultant force on the ship itself in the direction indicated by FIG. 2 whereby the stern of the ship is pushed to starboard and the ship itself tends to turn to port. It should also be recognized that there is a principle in fluid mechanics which states that there is a force proportional to circulation which is at right angles to the oncoming flow. The existence of this phenomenon has been demonstrated experimentally by various means including particularly the Dunham article above mentioned.

In FIG. 3 is shown an alternate embodiment of the invention comprising a ship hull 21, an underbody 22, twin screws 23, and a rounded stern portion 24. Rounded stern portion 24, unlike rounded stern portion 14, is rotatably supported on a vertical axis 36 and has on its rearward wall a pair of gaps 25, 27. These gaps 25, 27 have positioned between them generally vertically disposed a guide vane 26. The gap 25 leads into one side of the center of the rotatable stern portion 24 from which there is a pipe 34 shown in a dotted line representation in FIG. 4 leading through a valve 30 to a suction pump 28 which in turn directs water through another valve 35 into a pair of plenums 29, 32. Plenums 29, 32 in turn force water out through gaps 31 between the rounded stern portion 24 and the underbody 22. Gap 27 leads into the other side of the center of portion 24 from which there is another pipe 33 leading also to valve 30. Valve 30 controls the suction on gaps 25 and 27 by controlling the rate of flow from each half of portion 24.

The operation of the embodiment of FIGS. 3 and 4 is somewhat similar to that of FIGS. 1 and 2. The gaps 31 are of constant width and the flow of water issuing from them is a function of the pressure in the plenum chambers 29, 32 behind them. However, since rounded stern portion 24 is rotatable, the actual position of the gap 25 with respect to the stern of the ship is variable. In FIG. 4, gaps 25 and 27 and guide vane 26 are shown positioned to the port side of the ship. Water issuing from gaps 31 tends to proceed around both sides of rounded stern portion 24 until it encounters guide vane 26 and gap 25 whereupon a portion of it is drawn into the center of rotatable stern portion 24. Note that water is drawn only into gap 25 in this case, as it would be drawn only into gap 27 if the turn was to the opposite direction. The main purpose is to control the circulation of the main water flow around the rounded stern, thereby generating a lateral force. In this embodiment this is done mainly by the combination of a suction slot close to a vane with sharp trailing edge. Only a circulatory flow is in equilibrium with the conditions imposed on the fluid by such a conbination. At the same time it is necessary to prevent flow separation, which is accomplished by blowing out of slot 31.

The embodiment in FIGS. 3 and 4 may be employed in more than one way. The vane 26 may be situated dead astern and the steering force exerted by using the blowing and suction means on only one side. Alternatively, the vane may be rotated to one side as shown, and the blowing and suction made equal on both sides, as if there were only a single chamber within portion 24 and a single plenum behind it. In yet another variation, the vane may be used rotatably without the suction, to locate the stagnation point or line to one side, which will direct the circulation to that side.

The embodiment shown in FIGS. 3 and 4 has the added advantage that the water entering gaps 25 as well as the water directed through suction pump 28 tends to a very great extent to be water that has been recirculated through the system rather than sea water encountered by the ship in its passage through the ocean. As a consequence, the water passing through the suction pump 28 tends to be far cleaner than the run of water normally encountered in passage through the ocean having already been filtered several times through filters which are conventionallly provided in pumps 28.

The foregoing device for locating the stagnation point on the stern of a ship with a relatively low quantity of water flow, succeeds in directing the flow of a much larger volume of water and in addition, the horsepower required to issue this low volume of water from the gaps is not lost since it contributes to the propulsion of the ship. Additionally, since the flow of water in this manner around the stern of the ship significantly decreases the boundary layer separation of the main flow of water around the stern of the ship, a significant decrease in drag on the passage of the ship may be expected. In addition, the complex and cumbersome me chanical linkage normally required to operate the conventional rudder is done away with. The controls necessary to control passage of water through valve 17 are far less complex. In particular, rounded stern member 24 can have far less resistance to its rotation within underbody 22 than a conventional rudder, and consequently may be expected to have fewer problems in terms of durability and controllability.

I claim:

1. A steering control system for a ship, said ship having a rounded stern and lacking a conventional rudder, in which the water flowing past said stern has a symmetrical flow under balanced conditions, said system comprising:

a. a first generally vertically disposed slot impelling l water from inside said ship along a side of said ship rearwardly around one side of said stern,

b. a second generally vertically disposed slot impelling water from inside said ship along the other side of said ship rearwardly around the other side of said stern,

c. means to control the pressure on the water forward of each slot so as to cause relatively greater flow through one of said slots, whereby to cause relatively greater circulation of water around that side of said stern, and

d. suction means on the stern of said ship to draw in a portion of the water flowing around the stern of said ship, said suction means being positionable around the stem to control the flow of water to one side.

2. A steering control system as recited in claim 1, further comprising a guide vane on the stern of said ship at said suction means to guide flow of water into said suction means.

3. A steering control system as recited in claim 2, wherein said suction means comprises a suction opening on each side of said vane, each suction opening being separately connected controllably to a source of suction.

4. A steering control system as recited in claim 1, whereby the water drawn through said source of suction is returned to said means to control the pressure on each plenum.

5. A steering control system for a ship, said ship having a rounded stern and lacking a conventional rudder, in which the water flowing past said stern has a symmetrical flow under balanced conditions, said system comprising:

a. a first generally vertically disposed slot impelling water from inside said ship along a side of said ship rearwardly around one side of said stern,

b. a second generally vertically disposed slot impelling water from inside said ship along the other side of said ship rearwardly around the other side of said stern,

0. means to control the pressure on the water forward of each slot so as to cause relatively greater flow through one of said slots, whereby to cause relatively greater circulation of water around that side of said stern,

d. a rotatable means on the stern of said ship, said slots being formed between said rotatable means and the side of said ship, and

e. a guide vane vertically positioned on said rotatable means.

6. A steering control system for a ship, said having a rounded stern and lacking a conventional rudder, in which the water flowing past said stern has a symmetrical flow under balanced conditions, said system comprising:

a. a first generally vertically disposed slot impelling water from inside said ship along a side of said ship rearwardly around one side of said stern,

b. a second generally vertically disposed slot impelling water from inside said ship along the other side of said ship rearwardly around the other side of said stern,

c. means to control the pressure on the water forward of each slot so as to cause relatively greater flow through one of said slots, whereby to cause relatively greater circulation of water around that side of said stern,

d. a guide vane vertically positioned on the center line of the stern of said ship,

e. a suction opening on each side of said vane,

f. means to control the suction separately on each opening, and

g. a source of suction drawing water from each of said means to control the suction and returning it to said means to control the pressure. 

1. A steering control system for a ship, said ship having a rounded stern and lacking a conventional rudder, in which the water flowing past said stern has a symmetrical flow under balanced conditions, said system comprising: a. a first generally vertically disposed slot impelling water from inside said ship along a side of said ship rearwardly around one side of said stern, b. a second generally vertically disposed slot impelling water from inside said ship along the other side of said ship rearwardly around the other side of said stern, c. means to control the pressure on the water forward of each slot so as to cause relatively greater flow through one of said slots, whereby to cause relatively greater circulation of water around that side of said stern, and d. suction means on the stern of said ship to draw in a portion of the water flowing around the stern of said ship, said suction means being positionable around the stern to control the flow of water to one side.
 2. A steering control system as recited in claim 1, further comprising a guide vane on the stern of said ship at said suction means to guide flow of water into said suction means.
 3. A steering control system as recited in claim 2, wherein said suction means comprises a suction opening on each side of said vane, each suction opening being separately connected controllably to a source of suction.
 4. A steering control system as recited in claim 1, whereby the water drawn through said source of suction is returned to said means to control the pressure on each plenum.
 5. A steering control system for a ship, said ship having a rounded stern and lacking a conventional rudder, in which the water flowing past said stern has a symmetrical flow under balanced conditions, said system comprising: a. a first generally vertically disposed slot impelling water from inside said ship along a side of said ship rearwardly around one side of said stern, b. a second generally vertically disposed slot impelling water from inside said ship along the other side of said ship rearwardly around the other side of said stern, c. means to control the pressure on the water forward of each slot so as to cause relatively greater flow through one of said slots, whereby to cause relatively greater circulation of water around that side of said stern, d. a rotatable means on the stern of said ship, said slots being formed between said rotatable means and the side of said ship, and e. a guide vane vertically positioned on said rotatable means.
 6. A steering control system for a ship, said having a rounded stern and lacking a conventional rudder, in which the water flowing past said stern has a symmetrical flow under balanced conditions, said system comprising: a. a first generally vertically disposed slot impelling water from inside said ship along a side of said ship rearwardly around one side of said stern, b. a second generally vertically disposed slot impelling water from inside said ship along the other side of said ship rearwardly around the other side of said stern, c. means to control the pressure on the water forward of each slot so as to cause relatively greater flow through one of said slots, whereby to cause relatively greater circulation of water around that side of said stern, d. a guide vane vertically positioned on the center line of the stern of said ship, e. a suction opening on each side of said vane, f. means to control the suction separately on each opening, and g. a source of suction drawing water from each of said means to control the suCtion and returning it to said means to control the pressure. 